In multiple color printing it is necessary to produce halftone separation images to be used in making printing plates corresponding to each color ink to be printed. In a traditional four color printing process red, green and blue halftone separations are used to make cyan, magenta and yellow printers, respectively, and a black halftone separation is used to make a black printer.
Halftone separations may be produced on a camera by exposing original color artwork through color separation filters and appropriate halftone screens having the desired screen angles and screen pitch. This method permits relatively inexpensive production of halftone separations, but is tedious, time consuming, requires extensive training and is subject to numerous operator errors. With the advent of reliable electronic scanners, halftone separations for multiple color printing are rarely, if ever, produced on a camera.
Today, it is common to send original artwork to a color separation house which, for a fee, produces color separations using an electronic color scanner. The color scanner typically includes a rotating scanning drum for analyzing original artwork and an electronic dot generator for exposing halftones. In operation, the color scanner scans original color artwork to obtain red, green and blue channel information, processes the information, and electronically exposes cyan, magenta, yellow and black halftone separations. Available electronic color scanners typically utilize a laser dot generator to expose the halftone separations onto film wrapped around a rotating exposure drum. Unfortunately, electronic color scanners are very complex and require substantial training and experience to operate. Electronic color scanners are also very expensive, which makes them economically unfeasible for most printers interested in producing color halftone separations, resulting in the common practice to contract this service to a color separation house.
Therefore, it is one object of the invention to provide a relatively inexpensive color separation scanner for producing halftone color separations.
It is a further object of the present invention to provide a low cost color scanner that is relatively simple to operate.
It is another object of the present invention to provide a low cost color scanner with an electronic dot generator not including a laser light source.
These and other highly desirable and unusual results are accomplished by the present invention in a low cost color scanner structure that is relatively simple to operate and which achieves quality halftone separations.
Objects and advantages of the invention are set forth in part herein and in part will be readily appreciated herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.